|Shapiro Ilan, David|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2005
Publication Date: 8/1/2005
Citation: Shapiro Ilan, D.I., Stuart, R.J., Mccoy, C.W. 2005. Targeted improvement of steinernema carpocapsae for control of the pecan weevil, curculio caryae (horn) (coleoptera: curculionidae) through hybridization and bacterial transfer. Biological Control. 34:215-221. Interpretive Summary: The pecan weevil is a devastating pest of pecans. We are seeking new environmentally sound methods of controlling this pest. Insect-killing nematodes (small round worms) are one control method we are investigating. These nematodes kill insect pests with the help of bacteria that are carried inside the nematode. The nematodes and bacteria don’t harm people or the environment. The nematode’s success in killing pecan weevils relies heavily on which strain is used. We are developing improved nematode strains for pecan weevil control. In this study, we created superior strains by matching the best bacteria with the best nematode, and by hybridizing the strains (i.e., controlled mating). The new improved strains exhibited a high level of virulence (killing power) as well as a high degree of environmental tolerance to heat and desiccation. These strains will now be field tested to determine their efficacy under field conditions.
Technical Abstract: The entomopathogenic nematode Steinernema carpocapsae has shown promise for control of adult stage pecan weevil, Curculio caryae, a key pest of pecan. Our objective was to determine the feasibility of developing improved strains of S. carpocapsae by transferring the nematode’s bacterial symbiont (Xenorhabdus nematophila) from the Italian strain (which is highly virulent but has poor environmental tolerance) to the less virulent but more environmentally tolerant DD-136 strain, and through hybridization between the two wild type nematodes. Three modified strains were created: one through bacterial transfer alone and two hybrids through controlled crosses. We hypothesized that the improvement approaches would result in strains possessing high levels of environmental tolerance similar to DD-136 and virulence similar to the Italian strain. The hypothesis was supported in two out of three modified strains. Overall, the results indicate that bacterial transfer and hybridization could be a valuable tool in improving biocontrol efficacy of steinernematids.